Corrosion inhibited compositions



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United States Patent 0. F

CORROSION INHIBITED COMPOSITIONS Ellis K. Fields, Chicago, Ill., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana No Drawing. Application December 22, 1955 Serial No. 554,626

19 Claims. (Cl. 252-46.7)

This invention relates to improved compositions which are effective corrosion inhibitors and which are noncorrosive to silver, silver alloys and similar metals. More particularly, the invention pertains to lubricant compositions which are non-corrosive to such metals and inhibit the corrosion thereof by sulfur and/or corrosive sulfurcontaining compounds.

Advances in the design and construction of internal combustion engines aimed at increased efficiency and economy have led to lubricating problems. To meet the increased severe demands upon engines, many types of lubricant additives have been developed to obtain certain desired characteristics. Among the more elfective addition agents which have been developed for compounding with lubricants are many sulfur-containing organic compounds, such as sulfurized terpenes, sulfurized hydrocarbon oils, vegetable oils or animal oils, xanthate esters, organic polysulfides, particularly polyalkyl polysulfides, metal salts of organo-substituted thioacids of phosphorus, metal salts of the reaction product of a phosphorus sulfide and a hydrocarbon, such as for example, polybutenes and other polyolefins, and combinations of the foregoing.

Recent increased use of silver and similar metals in the construction of improved internal combustion engines has created new problems in the use of sulfur-containing additives in lubricants for such engines; the primary problem created being the corrosion of such silver parts of the engine by the sulfur-containing additives. While such corrosion can be eliminated by avoiding the use of sulfur-containing additives in lubricants for such engines, this solution of the problem is accompanied by the loss of the highly desired beneficial effects of the additives of this type.

It is an object of the present invention to provide a noncorrosive composition. Another object of the invention is to provide a composition non-corrosive to silver and similar metals. A further object of the invention is to provide a composition which will inhibit the corrosion of silver and similar metals by sulfur and/ or organic sulfurcontaining compounds. A still further object of the invention is to provide a lubricant composition which is non-corrosive. Still another object of the invention is to provide a lubricant composition containing an addition agent which will inhibit the corrosion of silver and similar metals by sulfur and/or organic sulfur-containing compounds. A further object of the invention is to provide a method of inhibiting the corrosion of silver and similar metals. Still another object of the invention is to provide a method of lubricating internal combustion engines containing silver and similar metal parts and inhibiting the corrosion of such metals by lubricants which contain sulfur and/or organic sulfur-containing compounds.

In accordance with the present invention, the foregoing objects can be attained by employing in oleaginous materials corrosion inhibiting amounts, viz., from about 0.02% to about and preferably from about 0.25% to about 2,910,439 Patented Oct. 27, 1959 5%, of an oil-soluble or oil-dispersible amine salt of 2,5 dimercapto-1,3,4-thiadiazole having the general formula s R H in which Y is hydrogen or the amino radical in which R is an aliphatic, aromatic or heterocyclic group and R and R can be aliphatic, aromatic or heterocyclic groups containing from about 6 to about 60 carbon atoms, and preferably at least about 14 carbon atoms, or hydrogen. R, R and R can be the same or different hydrocarbon or heterocyclic groups.

The amine employed in preparing the amine salt of 2,5-dimercapto-1,3,4-thiadiazole can be an aliphatic or aromatic monoor polyamine, and can be primary, secondary or tertiary amines, or can be basic ring nitrogen compounds containing 6 to 60, and preferably at least 14, carbon atoms. The amines can be commercially pure single compounds or can be mixtures of amines. Examples of suitable amines are hexylamine, dibutylamine, octylamine, nonylamine, dodecylamine, hexadecylamine, octadecylamine, cyclohexylamine, n-b'utylcyclohexylamine, dibenzylamine, furfurylamine, pyridines, quinolines, ethylene diamine, propylene diamine, diethylene triamine, diamylene triamine, triethylene tetramine, diethylene propylene triamine, tetraethylene pentamine, and mixtures of the foregoing. A suitable polyamine product is a crude diethylene triamine containing minor amounts of ethylene diamine and triethylene tetramine. Other suitable aliphatic polyamines include those having the general formula RNH(CH NH in which R is preferably a C to C aliphatic chain, and which are obtained by condensing the suitable amine with acrylonitrile and hydrogenating to the corresponding diamine. Commercially available aliphatic polyamines of this type are those marketed by Armour and Company as Duomeens, which are prepared by the condensation of a dodecyl (coco) amine or an octadecyl (tallow) amine with acrylonitrile followed by hydrogenation to the corresponding diamine product; these products are marketed as Duomeen C and Duomeen T, respectively. I may also employ aromatic polyamines, such as for example, phenylenediamine, and aliphatic amines, preferably those containing at least 8 carbon atoms in the alkyl group.

The amines may be chemically pure products or of a commercial quality. I have found as a desirable aliphatic amine, the amine residue obtained in the following process. Fatty acids, derived from natural fatty acid glycerides, are converted into nitriles and the nitriles are reduced, principally to primary amines, at temperatures below C. and under alkaline conditions. The reaction mass is then distilled, leaving a residue comprising essentially 10-25% primary amines and 30-60% secondary amines. Depending upon the fatty acid employed, the aliphatic amines usually contain from about 8 to about 18 carbon atoms. Suitable amine residues are the products manufactured according to this general procedure and sold by Armour and Company under the trade name, Armeen Residues. These residues are obtained as distillation residues in the manufacture of products sold by Armour and Company under the trade names Armeen CD, Armeen SD, Armeen 8D, Armeen 12D, Armeen 18D, etc. Armeen CD and Armeen SD are mixtures of primary amines prepared from coconut oil and soy bean oil, respectively, and other *Armeens" are mixtures of primary amines containing predominantly the number of carbon atoms specified in the trade name.

The amine salts of 2,5-dimercapto-l,3,4-thiadiazole can be readily prepared by stirring and heating a mixture of the dimercapto-thiadiazole and the amine until a homogeneous product is obtained. The molar proportions of amine to thiadiazole can be 1:1 to 2: 1, although the proportions up to 4:1 can be used to impart additional solubility to the salt. Solvents such as benzene or alcohol can be used to facilitate the salt formation.

The preparation of the amine salts is illustrated by the following examples:

EXAMPLE I A mixture of 53.8 grams (0.2 mole) of a mixture of tertiary alkyl primary amines with an average of 18 carbon atoms (marketed by Rohm and Haas as Alkylamine JMR), and 15 grams (0.1 mole) 2,5-dimercapto-l,3,4-thiadiazole was stirred at 110 C. for one hour and an oil-soluble viscous red product having a sulfur content of 12.7% and a nitrogen content of 6.05% was obtained.

EXAMPLE III A mixture of 60 grams (0.4 mole) 4-n-amyl pyridine and 30 grams (0.2 mole) 2,5-dimercapto-1,3,4-thiadiazole was stirred and heated at 130 C. until a clear solution was obtained. On cooling, a dark yellow crystalline mass having a melting point of 120130 C., a sulfur content of 22.1% and a nitrogen content of 12.42% was obtained. Calculated for C H S N -sulfur=21.5% and N=12.51%.

EXAMPLE IV A mixture of 22.5 grams (0.15 mole) of 2,5-dimercapto-1,3,4-thiadiazole, 40.4 grams (0.15 mole) of Armeen T and 30 cubic centimeters ethylene glycol dimethyl ether was stirred at 110 C. till all the solvent had evaporated and a clear liquid product obtained. The resultant product (yield 62 grams) which solidified on cooling contained 8.97% nitrogen and 20.6% sulfur.

The Armeen T is a mixture of aliphatic amines marketed by Armour and Company and obtained by converting tallow fatty acids to nitriles and reducing the resulting nitriles at temperatures below 150 C. under alkaline conditions. The reaction mass is then distilled, leaving a residue of principally primary amines.

EXAMPLE V A mixture of 15 grams (0.1 mole) of 2,5-dimercapto- 1,3,4-thiadiazole, 42.1 grams (0.1 mole) of tallow amine bottoms (3.55% nitrogen and 421 molecular weight) and 30 cubic centimeters ethylene glycol dimethyl ether was stirred at 110 C. until all of the solvent had evaporated and a clear liquid product obtained. The resultant product (yield 57 grams) which solidified on cooling contained 7.37% nitrogen and 17.0% sulfur.

EXAMPLE VI A mixture of 22.5 grams (0.15 mole) 2,5-dimercapto- 1,3,4-thiadiazole, 40.4 grams (0.15 mole) of a mixture of tertiary alkyl amines with an average of 18 carbon atoms (marketed by Rohm and Haas as Primene JMR) and 30 cubic centimeters of ethylene glycol dimethyl ether was stirred at 110 C. until all of the solvent had evaporated. Sixty-two grams of a clear yellow viscous liquid product which contained 9.13% nitrogen and 21.7% sulfur was obtained.

The above-described amine salts can be used in amounts of from about 0.02% to about 10%, and preferably from about 0.25% to about 5%, in combination with lubricant base oils, such as hydrocarbon oils, synthetic hydrocarbon oils, such as those obtained by the polymerization of hydrocarbons, such as olefin polymers, for example, polybutenes, polypropylene and mixtures thereof, etc.; synthetic lubricating oils of the alkyleneoxide type, for example, the Ucon oils, marketed by Carbide and Carbon Corporation, as well as other synthetic oils, such as the polycarboxylic acid ester-type oils, such as the esters of adipic acid, sebacic acid, maleic acid, azelaic acid, etc.

While the above described amine salts can be suitably employed alone in combination with a base oil, they are usually used in combination with other lubricant addition agents, which impart various desired characteristics to the base oil. Usually these amine salts are used in conjunction with detergent-type additives, particularly those which contain sulfur, or phosphorus and sulfur. Such detergent-type additives are used in amounts of from about 0.002% to about 10%, and preferably from about 0.01% to about 5%. Among the phosphorus and sulfurcontaining addition agents are the neutralized reaction products of a phosphorus sulfide and a hydrocarbon, an alcohol, a ketone, an amine or an ester. Of the phosphorus sulfide reaction product additives, we prefer to employ the neutralized reaction products of a phosphorus sulfide, such as a phosphorus pentasulfide, and a hydrocarbon of the type described in U.S. 2,316,082, issued to C. M. Loane et al., April 6, 1943. As taught in this patent, the preferred hydrocarbon constituent of the reaction is a mono-olefin hydrocarbon polymer resulting from the polymerization of low molecular Weight monoolefin hydrocarbons, such as propylenes, butenes, amylenes, or copolymers thereof. Such polymers may be obtained by the polymerization of mono-olefins of less than 6 carbon atoms in the presence of a catalyst, such as sulfuric acid, phosphoric acid, boron fluoride, aluminum chloride, or other similar halide catalysts of the Friedel-Crafts type.

The polymers employed are preferably mono-olefin polymers or mixtures of mono-olefin polymers and isomono-olefin polymers having molecular weights ranging from about 150 to about 50,000 or more, and preferably from about 500 to about 10,000. Such polymers canbe obtained, for example, by the polymerization in the liquid phase of a hydrocarbon mixture containing mono and isomono-olefins, such as butylene and isobutylene at a temperature of from about F. to about F. in the presence of a metal halide catalyst of the Friedel- Crafts type such as, for example, boron fluoride, aluminum chloride, and the like. In the preparation of these polymers, a hydrocarbon mixture containing isobutylene, butylenes and butanes recovered from petroleum gases, especially those gases produced in the cracking of petroleum oils, in the manufacture of gasoline, can be used.

Another suitable polymer is that obtained by polymerizing in the liquid phase, a hydrocarbon mixture comprising substantially C hydrocarbons in the presence of an aluminum chloride-complex catalyst. The catalyst is preferably prepared by heating aluminum chloride with isooctane. The hydrocarbon mixture is introduced into the bottom of the reactor and passed upwardly through the catalyst layer, while a temperature of from about 50 F. to about F. is maintained in the reactor. The propane and other saturated gases pass through the catalyst, while the propylene is polymerized under these conditions. The propylene polymer can be fractionated I to any desired molecular weight, preferably from about 500 to l000, or higher.

Other suitable polymers are those obtained by polymerizing a hydrocarbon mixture containing about 10% to about 25% isobutylene at a temperature of from about F. to about 100 F., and preferably 0 F. to about 32 F. in the presence of boron fluoride. After the polymerization of the isobutylene, together with a relatively minor amount of the normal olefins present, the reaction mass is neutralized, washed free of acidic substances and the unreacted hydrocarbons subsequently separated from the polymers by distillation. The polymer mixture so obtained, depending upon the temperature of reaction, varies in consistency from a light liquid to viscous oily material and contains polymers having molecular weights ranging from about 100 to about 2000, or higher. The polymers so obtained may be used as such, or the polymer may be fractionated under reduced pressure into fractions of increasing molecular weights, and suitable fractions obtained reacted with the phosphorus sulfide to obtain the desired reaction products. The bottoms resulting from the fractionation of the polymer which have Saybolt Universal viscosities at 210 F., rang ing from about 50 seconds to about 10,000 seconds, are well suited for this purpose.

Essentially parafiinic hydrocarbons, such as bright stock residuums, lubricating oil distillates, petrolatums, or paraifin waxes, may be used. There can also be employed the condensation products of any of the foregoing hydrocarbons, usually through first halogenating the hydrocarbons with aromatic hydrocarbons in the presence of anhydrous inorganic halides, such as aluminum chloride, zinc chloride, boron fluoride, and the like.

Examples of other high molecular weight olefinic hydrocarbons which can be employed are cetene (C cerotene (C melene (C and mixed high molecular weight alkenes obtained by cracking petroleum oils.

Other preferred olefins suitable for the preparation of the phosphorus sulfide reaction products are olefins having at least 20 carbon atoms in the molecule of which from about 13 carbon atoms to about 18 carbon atoms, and preferably at least 15 carbon atoms are in a long chain. Such olefins can be obtained by the dehydrogenation of alkyl halides, preferably long chain alkyl halides, particularly halogenated parafiin waxes.

As a starting material there can be used the polymer or synthetic lubricating oil obtained by polymerizing unsaturated hydrocarbons resulting from the vapor phase cracking of paramn waxes in the presence of aluminum chloride which is fully described in United States Patents Nos. 1,955,260, 1,970,402 and 2,091,398. Still another type of olefin polymer which may be employed is the polymer resulting from the treatment of vapor phase cracked gasoline and/or gasoline fractions with sulfuric acid or solid adsorbents, such as fullers earth, whereby unsaturated polymerized hydrocarbons are removed. The reaction products of the phosphorus sulfide and the polymers resulting from the voltolization of hydrocarbons as described, for example, in United States Patents Nos. 2,197,768 and 2,191,787 are also suitable.

Other hydrocarbons that can be reacted with a phosphorus sulfide are aromatic hydrocarbons, such as for example, benzene, naphthalene, toluene, xylene, diphenyl, and the like, or with the an alkylated aromatic hydrocarbon, such as for example, benzene having an alkyl substituent having at least four carbon atoms, and preferably at least eight carbon atoms, such as a long chain parafiin wax.

The phosphorus sulfide-hydrocarbon reaction product can be readily obtained by reacting a phosphorus sulfide, for example, P 8 with the hydrocarbon at a temperature of from about 200 F. to about 500 F., and preferably from about 200 F. to about 400 F., using from about 1% to about 50%, and preferably from about 5% to about 25% of the'phosphorus sulfide in the reaction. It is advantageous to maintain a non-oxidizing atmosphere, such as for example, an atmosphere of nitrogen above thereaction mixture. Usually, it is preferable to use an amount of the phosphorus sulfide that will completely react with the hydrocarbon so that no further purification becomes necessary; however, an excess amount of phosphorus sulfide can be used and separated from the product by filtration or by dilution with a hydrocarbon solvent, such as hexane, filtering and subsequently removing the solvent by suitable means, such as by distillation. If desired, the reaction product can be further treated with steam at an elevated temperature of from about F. to about 600 F.

The phosphorus sulfide-hydrocarbon reaction product normally shows a titratable acidity which is neutralized by treatment wtih a basic reagent. The phosphorus sulfide-hydrocarbon reaction product, when neutralized with a basic reagent, containing a metal constituent, is characterized by the presence or retention of the metal constituent of the basic reagent.

The neutralized phosphorus sulfide-hydrocarbon reaction product can be obtained by treating the acidic reaction product with a suitable basic compound, such as hydroxide, carbonate, oxide or sulfide of an alkaline earth metal or an alkali metal, such as for example, potassium hydroxide, sodium hydroxide, sodium sulfide, calcium oxide, lime, barium hydroxide, barium oxide, etc. Other basic reagents can be used, such as for example, ammonia or an alkyl or aryl-substituted ammonia, such as amines. The neutralization of the phos phorus sulfide-hydrocarbon reaction product is carried out preferably in a non-oxidizing atmosphere by contacting the acidic reaction product either as such or dissolved in a suitable solvent, such as naphtha with a solution of the basic agent. As an alternative method, the reaction product can be treated with solid alkaline compounds, such as KOH, NaOH, Na CO K CO CaO, BaO, Ba(OH) Na S, and the like, at an elevated temperature of from about 100 F. to about 600 F. Neutralized reaction products containing a heavy metal constituent, such as for example, tin, titanium, aluminum, chromium, cobalt, zinc, iron, and the like, can be obtained by reacting a salt of the desired heavy metal with the phosphorus sulfide-hydrocarbon reaction product, which has been treated wtih a basic reagent, such as above-described.

Other phosphorus sulfide reaction products which can be used are the reaction products of a phosphorus sulfide and a fatty acid ester of the type described in US. 2,399,243; the phosphorus sulfide-degras reaction products of US. 2,413,332; the reaction product of an al- =kylated phenol wtih the condensation product of P 8 and turpentine of US. 2,409,877 and US. 2,409,878; the reaction product of a phosphorus sulfide and a stearonitrile of US. 2,416,807, etc.

The silver corrosion inhibiting property of the above described amine salts is demonstrated by the data in Table I, which were obtained by subjecting mixtures of hydrocarbon oil, a neutralized reaction product of P 8 and a polybutene, and various amine salts of 2,5-dimercapto-1,3,4-thiadiazole to the following test, hereinafter referred to as the modified EMD test:

A silver strip 2 cm. x 5.5 cm. with a small hole at one end for suspension, is lightly abraded with No. 0 steel wool, wiped free of any adhering steel wool, washed with carbon tetrachloride, air-dried and then weighed to 0.1 milligram. 300 cc. of the oil to be tested is placed in a 500 cc. lipless glass beaker and the oil heated to a temperature of 300 F. (i2 F.) and the silver strip suspended in the oil so that the strip is completely immersed therein. The oil in the beaker is stirred by means of a glass stirrer operating at 300 rpm. At the end of twenty-four hours, the silver strip is removed, and while still hot, rinsed thoroughly with carbon tetrachloride and air-dried. The appearance of the strip is then visually noted and given ratings according to the following scale:

7 1Bright 2-Sta ined 3-Grey-black 4- Black, smooth 5Black, flake After the visual inspection, the silver strip is immersed hrs potassium cyanide solution at room temperature until the silver surface assumes its original bright or silver appearance. The silver strip is then washed successively with distilled water and acetone, air-dried, weighed. The visual inspection may be dispensed with if desired.

The following lubricant compositions were subjected to the above test and the results obtained tabulated in Table I:

Table I Silver corrosion (EMD test) (mg. Weight loss/ appearance) Sample Obi? Since a weight loss of less than 20 milligrams is desirable, the ability of the amine salts of 2,5-dimercaptol,3,4,-thiadiazole of this invention to inhibit silver corrosion is demonstrated by the above data.

The effectiveness of the herein-described thiadiazole reaction products in inhibiting corrosion toward copper and/or lead-containing metals, such as for example, copper-lead alloys, is demonstrated by the data in Table II, obtained by subjecting lubricants containing the additive to the following test:

.A copper-lead test specimen is lightly abraded with steel wool, washed with naphtha, dried and Weighed to the nearest milligram. The cleaned copper-lead test specimen is suspended in a steel beaker, cleaned with a hot trisodium phosphate solution, rinsed with water, acetone and dried, and 250 grams of the oil to be tested, together with 0.625 gram lead oxide and 50 grams of a 3035 mesh sand charged to the beaker. The beaker is then placed in a bath or heating block and heated to a temperature of 300 F. t2 F.) while the contents are stirred by means of a stirrer rotating at 750 r.p.m. The contents of the beaker are maintained at this temperature for twenty-four hours, after which the copper-lead test specimen is removed, rinsed with naphtha, dried and weighed. The test specimen is then replaced in the beaker and an additional 0.375 gram of lead oxide added to the test oil. At'the end of an additional twenty-four hours of test operation the test specimen is again removed, rinsed and dried as before, and weighed. The test specimen is again placed in the beaker, together with an additional 0.250 gram of lead oxide, and the test continued for another twenty-four hours (seventy-two hours total). At the conclusion of this time, the test specimen is removed from the beaker, rinsed in naphtha, dried and weighed.

The loss in weight of the test specimen is recorded after each weighing.

This test, known as the Stirring Sand Corrosion Test, is referred to hereinafter as SSCT.

The following samples were subjected to the above test and the results tabulated in Table II.

Sample AControl (solvent-extracted SAE-30 oil +33% barium-containing neutralized reaction product of P 8 and a polybutene of about 1000 molecular Weight).

Sample B'A+0.75 product of Example I.

Sample (Y-A +0.75% product of Example 11.

Sample -D-A+l.0% product of Example 'IV.

Since Weight losses of 200 milligrams in 48 hours and 500 milligrams in 72 hours are allowable, the copper-lead inhibiting property of the herein-described amine salts of 2,5-dimercapto-1,3,4-thiadiazole is clearly demonstrated by the above data.

Under certain conditions, it is desirable to use in lubricant compositions from about 0.01% to about 5%, and preferably from about 0.1% to about 2%, elemental sulfur or an organic sulfur-containing compound of the type hereinabove described either alone or in combination with other additives. Eflective lubricant compositions are obtained by the combination of the neutralized reaction products of a phosphorus sulfide and a hydrocarbon, as above described, with elemental sulfur, or an organic sulfur-containing compound, such as sulfurized mineral oils, sulfurized non-drying animal and vegetable oils, sulfurized olefins and olefin polymers, sulfurized sperm oil, etc., as described and claimed in U.S. Reissue 22,464, issued to C. D. Kelso et al. April 4, 1944, or with sulfurized terpenes, for example, dipentene, as described and claimed in U.S. 2,422,585, issued to T. H. Rogers et al. June 17, 1947. While these compounds impart highly desired characteristics to lubricants, and effectively inhibit the corrosion of copper and/or lead, they are, under some conditions, corrosive to silver and similar metals, and for this reason, lubricants containing such addition agents fail to pass the above-described EMD Test. In accordance with the present invention, however, the incorporation in such lubricant compositions of small amounts, namely, from about 0.1% to about 10%, and preferably from about 0.25% to about 5%, of amine salts of 2,5- dimercapto-l,3,4-thiadiazole, effectively inhibits the corrosiveness of the silver-corrosive compounds Without impairing their other desired properties.

The ability of the amine salts of 2,5-dimercapto-l,3,4- thiadiazole to inhibit the silver corrosion tendency of active sulfur-containing organic compounds is demonstrated by the following EMD data in Table III, obtained with the following compositions:

Table 111 Silver corro- I Sample sion (mg.

weight loss) 9 Since a weight loss of less than 20 milligrams is desirable, the ability of the products of the present invention to inhibit silver corrosion even in the presence of organic compounds corrosive to silver is demonstrated by the above data.

Although the invention has been described in connection with the use of the herein-described amine salts of 2,5-dimercapto-l,3,4-thiadiazole in combination with the one or more secondary additives in lubricant compositions, the invention is not restricted to such use, since these compounds find utility when used alone in various lubricant compositions or hydrocarbon oil compositions to impart improved and desired characteristics thereto. Thus, for example, these compounds may be used alone in hydrocarbon oils and fuels. In addition to their corrosion inhibiting property, they also are effective in inhibiting the oxidation of hydrocarbon oils as demonstrated by the data in Table IV, which were obtained by subjecting an SAE-3O oil containing products of the present invention to the above-described SSCT test, and to the following oxidation test herein-referred to as the ISOT. In this test, 250 cc. of the oil to be tested are heated at 330 F. to 332 F. in a 500 cc. glass beaker in the presence of 5 square millimeters of copper and 10 square millimeters of iron. Four glass rods of 6 millimeter diameter are suspended in the oil which is stirred at about 1300 rpm. by means of a glass stirrer. At intervals of 24, 48 and 72 hours, oil samples are taken and the percent of naphtha insolubles determined, and the glass rods visually inspected for evidence of varnish formation thereof. Varnish values are based on a visual rating in which a glass rod free of any varnish is given a rating of 10, while a badly coated rod is given a rating of 1. Rods having appearances between these extremes are given intermediate values.

The following samples were subjected to the above tests and the results tabulated in Table IV.

Sample A"'-Control (SAE30 oil-no additive). Sample B"'A+3.3 product of Example I. Sample C"'A"+2.0% product of Example IV. Sample D"'-A+2.0% product of Example V. Sample 'EA+2.0% product of Example VI.

Table IV SSCI" test mg. weight loss Sample 24 hrs. 48 hrs. 72 hrs.

ISOT test varnish rating ISOT test naphtha insoluble Percent Percent Percent 0. 129 5.0 6.

0. 029 0. 057 Trace cant composition's,their use is not limited thereto; but the same can be used in products other than lubricating oils, such as for example, fuel oils, insulating oils, greases, non-drying animal and vegetable oils, waxes, asphalts, and any fuels for internal combustion engines, partic ularly where sulfur corrosion must be combatted.

Concentrates of a suitable oil base containing more than 10% of an amine salt of 2,5-dimercapto1,3,4-thiadiazole alone or in combination with other additives can be used for blending with hydrocarbon oils or other oils in the proportions desired for the particular conditions of use torgive a finished product containing from 0.02% to about 10% of the amine salt.

Percentages given herein and in the appended claims are weight percentages unless otherwise stated.

This application is a continuation-in-part of my copending application Serial No. 349,959, filed April 20, 1953, now abandoned.

Although the present invention has been described with reference to specific preferred embodiments thereof, the invention is not to be considered as limited thereto but includes within its scope such modifications and variations as come within the spirit of the appended claims.

I claim:

1. A composition non-corrosive to silver and having silver corrosion inhibiting properties consisting essentially of a major proportion of an oil containing a compound normally corrosive to silver and from about 0.02% to about 10% of an oil-soluble amine salt of 2,5-dimercapto-1,3,4-thiadiazole having the general formula in which Y is selected from the class consisting of hydrogen and an amino radical Where R is selected from the group consisting of an aliphatic group, an aromatic group and a heterocyclic group, and R and R are selected from the group consisting of aliphatic groups, aromatic groups, heterocyclic groups and mixtures thereof, and hydrogen, said aliphatic, aromatic, and heterocyclic groups containing from about 6 to about 60 carbon atoms.

2. A composition non-corrosive to silver and having silver corrosion inhibiting properties consisting essentially of a major proportion of an oil containing a compound normally corrosive to silver and from about 0.02% to about 10% of an oil-soluble amine salt of 2,5-dimercapto-1,3,4-thiadiazole having the general formula e ra f) ya... an E I i S R H in which R is selected from the group consisting of an aliphatic group, an aromatic group and a heterocyclic group, and R and R are selected from the group consisting of aliphatic groups, aromatic groups, heterocyclic groups, mixtures thereof, and hydrogen, said aliphatic, aromatic and heterocyclic groups containing from about 6 to about 60 carbon atoms.

3. A composition as described in claim 2 in which the amine salt is an aliphatic amine salt.

4. A composition as described in claim 2 in which the amine salt is a salt of dodecyl amine.

5. A composition as described in claim 2 in which the amine salt is a salt of a mixture of secondary C and C amines.

6. A composition as described in claim 2 in which the amine salt is a salt of a tertiary alkyl primary amine having an average of about 18 carbon atoms.

7. A composition as described in claim 2 in which the amine salt is an aromatic amine salt.

8. A composition as described in claim 2 in which the amine salt is a salt of 4-n-amyl pyridine.

9.-A composition non-corrosive to silver and having silver corrosion inhibiting properties consisting essentially of a major proportion of an oil, from about 0.02% to about 10% of an oil-soluble amine salt of 2,5-dimercapto-l,3,4-thiadiazole, and from about 0.001% to about 10% of a sulfur-containing organic compound normally corrosive to silver, said amine salt having the general formula 5 in which R is selected from the group consisting of an aliphatic group, an aromatic group and a heterocyclic group, and R and R are selected from the group consisting of aliphatic groups, aromatic groups, heterocyclic groups, mixtures thereof, and hydrogen, said aliphatic, aromatic and heterocyclic groups containing from about 6 to about 60 carbon atoms.

10. A composition as described in claim 9 in which the amine salt is an aliphatic amine salt.

11. A composition as described in claim 9 in which the sulfur-containing organic compound is a sulfurized terpene.

12. A composition as described in claim 9 which contains from about 0.001% to about 10% of a phosphorusand sulfur-containing detergent-type lubricant additive.

13, A lubricant composition comprising a major proportion of a lubricating oil, from about 0.001% to about 10% of a phosphorousand sulfur-containing detergenttype lubricant additive and from about 0.02% to about 10% of an oil-soluble amine salt of 2,5-dimercapto-1,3,4- thiadiazole having the general formula in which Y is selected from the class consisting of hydrogen and an amino radical Where R is selected from the group consisting of an aliphatic group, an aromatic group and a heterocyclic group, and R and R are selected from the group consisting of aliphatic groups, aromatic groups, heterocyclic groups and mixtures thereof, and hydrogen, said aliphatic, aromatic, and heterocyclic groups containing from about 6 to about 60 carbon atoms.

14. A lubricant composition comprising a major proportion of a lubricating oil, from about 0.02% to about 10% of an oil-soluble amine salt of 2,5-dimercapto-1,3,4- thiadiazole, and from about 0.001% to about 10% of a 12 phosphorusand sulfur-containing detergent-type lubricant additive, said amine salt having the general formula in which R is selected from the group consisting of an aliphatic group, an aromatic group and a heterocyclic group, and R and R are selected from the group consisting of aliphatic groups, aromatic groups, heterocyclic groups, mixtures thereof, and hydrogen, said aliphatic, aromatic and heterocyclic groups containing from about 6 to about 60 carbon atoms.

15. A lubricant composition as described in claim 13 in Which the detergent-type lubricant additive is a neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

16. A lubricant composition as described in claim 13 in which the detergent-type lubricant additive is an alkali metal-containing neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

17. A lubricant composition as described in claim 13 in which the detergent-type lubricant additive is an alkaline-earth containing neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

18. A lubricant composition as described in claim 13 in which the detergent-type lubricant additive is a bariumcontaining neutralized reaction product of a phosphorus sulfide and a hydrocarbon.

19. An addition agent for lubricating oils comprising a concentrated solution of a hydrocarbon oil containing more than 10% of an oil-soluble amine salt of 2,5-dimercapto-l,3,4-thiadiazole, having the general formula in which Y is selected from the class consisting of hydrogen and an amino radical References Cited in the file of this patent UNITED STATES PATENTS Lowe Oct. 5, 1954 Fields Oct. 2, 1956 

1. A COMPOSITION NON-CORROSIVE TO SILVER AND HAVING SILVER CORROSION INHIBITING PROPERTIES CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF AN OIL CONTAINING A COMPOUND NORMALLY CORROSIVE TO SILVER AND FROM ABOUT 0.02% TO ABOUT 10% OF AN OIL-SOLUBLE AMINE SALT OF 2,5-DIMERCAPTO-1,3,4-THIADIAZOLE HAVING THE GENERAL FORMULA 